The invention concers a process for the treatment of radioactively contaminated waste water emitted from installations for chemically preparing uranium ores. Uranium, which principally finds application as fissionable material or nuclear fuel in modern atomic power plants, is obtained from uranium ore which at most contains only a fraction of one per cent of uranium.
In order to extract the uranium, the ore is subjected to a chemical treatment after some preliminary filtration and other mechanical steps. During such chemical treatment, which employs fresh water and in which gross quantities of auxiliary chemicals (e.g. acids during the ion exchange or adsorption operations for removing certain radioactive components) are used up extraordinarily large amounts of radioactively contaminated amounts of waste water are generated. The waste water emitted from installations of this type is in the form of aqueous solutions of inorganic salts, and also contains residual uranium and elements resulting from the decomposition of uranium, such as radium, polonium and lead. The treatment of such waste water to negate its dangers represents a difficult problem for each installation.
Two principal methods of such treatment have been commonly employed. In one, which has been used where natural water courses or streams occur in the vicinity of the installation, the waste water is further diluted with water and discharged into the stream, usually after some pre-treatment via ion exchange or adsorption. Such treatment, of course, leads to radioactive contamination and poisoning of the water course.
In the second commonly used treatment method, employed where there are no water courses in the vicinity of the chemical treatment installation, the waste water is collected in a natural, open settling tank. The spent ore is collected in the bottom portion of the settling tank, while the remainder of the waste water which forms the top layer, is fed back to the installation for reuse.
The principal disadvantage of this latter scheme is that its life is limited, since the concentration of salt in the waste water gradually climbs to an unacceptable limiting value beyond which a re-use of the water is no longer possible. Additionally, such settling tanks are expensive to maintain and, of course, exhibit the danger that the salts accumulating in the lower ground layers can leak out, leading again to contamination or poisoning.